The present invention relates to an instrument and method for particulate characterization in combustion exhausts, and more particularly relates to a method and portable instrument based on laser induced incandescence (LII) to measure particulate content and primarily mass emissions (gms/cm3) of combustion exhausts, such as from diesel engines.
Particles emitted from diesel engines pose a significant health hazard to the general public because these particles are of the right size to be inhaled and deposited deep inside the lungs. An additional concern is that certain substances that condense on the surface of these particles are carcinogenic.
Newer particulate standards imposed by the Environmental Protection Agency (EPA) have serious implications toward the future operation of combustion equipment. Current research efforts to curtail particulate emissions are limited by the lack of proper measurement techniques. The known measurement techniques require expensive instrumentation with equally matching demands on operator skill and time. One widely accepted EPA approved technique entails the collection of particulates using a filter paper in a diluted stream of exhaust gases, which is followed by gravimetry. Alternate measurement techniques are based upon light extinction or reflection principles. Efforts to obtain quantitative measurements based upon such principles have resulted in little success.
Techniques used in air sampling only are effectively used for measuring particle number concentrations, N (particles/cm3). However, large response-times, such as 120 seconds, preclude their use for transient evaluations.
Laser induced incandescence (LII), a recently developed technique facilitates real-time quantitative planar imaging of soot emissions. A doctoral thesis by Sreenath B. Gupta at Pennsylvania State University in December, 1996 entitled xe2x80x9cCHEMICAL MECHANISTIC APPROACHES TO SOOT CONTROL IN LAMINAR DIFFUSION FLAMESxe2x80x9d describes the use of laser induced incandescence (LII) in characterizing the soot field in flames.
It is an object of the invention to provide an improved instrument and method for particulate characterization in combustion exhausts.
It is another object of the invention to provide an improved method and instrument based on laser induced incandescence (LII) to measure particulate content and primarily mass emissions (gms/cm3) of combustion exhausts.
It is another object of the invention to provide an improved method and instrument based on laser induced incandescence (LII) to measure particulate content and primarily mass emissions (gms/cm3) of combustion exhausts during transient operation of an engine.
It is another object of the invention to provide such improved method and instrument for measuring particle size in nanometers and number density or number of particles per cubic centimeter and mass concentration or grams of particles per cubic centimeter (gms/cm3) of combustion exhausts during transient operation of an engine.
It is another object of the invention to provide such instrument that is a compact and portable device and that enables fast, easy, and cost-effective characterizing of particles of combustion exhausts.
It is another object of the invention to provide such improved method and instrument substantially without negative effect and that overcome many of the disadvantages of prior arrangements.
In brief, an improved instrument and method are provided for particulate characterization in combustion exhausts. An instrument for measuring particles of combustion exhausts includes a laser for producing a high intensity laser pulse. A sample cell receives a combustion exhaust input and the high intensity laser pulse. At least one detector detects a signal generated by particles in said received combustion exhaust input. The detected signal includes laser induced incandescence (LII).
In accordance with features of the invention, signal conditioning electronics is coupled to the detector and particle data is displayed during transient operation of a combustion engine. Data related to mass concentration, number density, and particle size of particles in the received combustion exhaust input is measured and displayed.